Although a strong association between ras activation and human carcinogenesis has been established, both the mechanism of oncogenic ras transformation and its contribution to the malignant process remain to be determined. The overall goal of the proposed research is the identification of the structural and biochemical properties of the ras proteins that are important for neoplastic transformation. The interaction between ras and other cellular components that may regulate ras biological activity will also be emphasized. The general approach will entail the generation of structural and functional mutants of the human ras proteins. Chimeric proteins will also be constructed between H-ras and ras-related proteins. These ras-related proteins will include the recently identified Krev-1 protein, which suppresses oncogenic ras transforming activity. The biological activities of these mutant ras proteins will be characterized by a variety of in vitro biological assays. Additional in vitro cell transformation systems will also be established to address the involvement of oncogenic ras in the transformation of cells of epithelial origin. Overall, these approaches should generate useful information for identifying the properties of the oncogenic ras that are responsible for the malignant transformation and altered differentiation.